// https://leetcode.cn/problems/delete-node-in-a-bst/
public class DelNode {
    private static class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;

        public TreeNode(int val) {
            this.val = val;
        }

    }
    class Solution {

        public TreeNode deleteNode(TreeNode root, int key) {
            if(root == null) return root;
            if(root.val == key)
            {
                if(root.left == null) return root.right;
                if(root.right == null) return root.left;
                TreeNode cur = root.right;
                while(cur.left != null){
                    cur = cur.left;
                }
                cur.left = root.left;
                root = root.right;
                return root;
            }
            if(root.val < key) root.right = deleteNode(root.right,key);
            if(root.val > key) root.left = deleteNode(root.left,key);
            return root;

        }
    }
}
